Reliability Upgrading of Long Period Component of Strong Ground Accelerograms and their Applications to Large Scale Structures

用SMAC加速度计测得的响应谱与其他地震仪测得的响应谱比较，前者在约5秒的周期范围内给出的值大于后者。将品川站记录的SMAC加速度谱与SAMTAC（数字式加速度计）的加速度响应谱进行了比较。在较短的周期范围内，两种谱几乎重合，但SMAC记录的响应谱与SAMTAC记录的响应谱差异较大。为了研究SMAC加速度计在较长周期范围内的记录特性，将SMAC加速度计与其他地震仪和位移仪在振动台上进行了振动。移位和波动在SMAC记录中引起，这些不希望的分量通常具有所谓的1/f谱形状。当一个SMAC由Hachinohe记录驱动时，记录笔在30秒左右的低频分量也有1/f的频谱形状，这是由笔的移动引起的。笔的移动和漂移是由连接摆和记录笔运动的连杆的缺陷和笔与纸之间的摩擦耦合引起的。这支笔用针推，用弹簧线圈拉。然而，当笔与纸之间的摩擦大于弹簧的刚度时，笔就不会被弹簧拉住。因此，笔被留在后面，记录被移动。因此，必须从每个记录中消除记录的漂移。在假设相位不变的情况下，从原始频谱中减去噪声分量的频谱。将所提出的修正方法应用于若干SMAC记录，并与位移型强震仪记录进行了比较。对加速度响应谱进行了比较，得到了满意的结果。

When response spectra determined from SMAC accelerograms are compared with that from other kind of seismographs, the former gives larger value for the period range over about 5 second than the latter. The response spectrum determined from a SMAC accelerogram recorded at Shinagawa is compared with the acceleration response spectrum from SAMTAC which is a digital type accelerograph. While both spcetra almost coincide for the shorter period range, the response spectrum for SMAC record quite differs from that for SAMTAC record.In order to investigate the recording characteristics of longer period range of SMAC accelerograph, a SMAC accelerograph was shaken on a shaking table with other seismometers and displacement meters. The shift and fluctuation are induced in a SMAC record and these undesirable components have commonly so-called 1/f spectral shape.When a SMAC was driven by the Hachinohe record, the recording pen was shifted at 30 second around low frequency component has also 1/f spectral shape and it is caused by the shift of the pen.The shift and drift of the pen is caused by a coupling between a defect of the link connecting the motion of the pendulum and recording pen and a friction between pen and paper. The pen is pushed by needle and pulled by a spring coil. However, when the friction between the pen and paper is greater than the stiffness of the spring, the pen is not pulled by the spring. Consequently the pen is left behind and the record is shifted. Therefore, the drift of record must be removerd from each record. A spectrum of noise component was subtracted from the original spectrum under the assumption that the phase remains unchanged.The proposed correction method was applied to a number fo SMAC records and results were compared with records obtained by strong motion seismometer of displacement type. Comparison was done on the acceleration response spectrum and the result was satisfactory.